title: Pressure and magnetic field dependence of valence and magnetic transitions in EuPtP.
abstract: The hexagonal layered compound, EuPtP, exhibits two valence transitions, at T₁ = 235 K and T₂ = 190 K, and an antiferromagnetic order at T(N) = 8.6 K. We have examined the effects of magnetic field and pressure, and the specific heat. Analysis of the high-field experiments confirms that half of Eu are in a divalent state at the lowest temperature, and that the number of Eu(² + ) increases discontinuously at T₂ and T₁ with increasing temperature. The magnetic entropy reaches ~ 22 J K⁻¹ mol⁻¹ at room temperature, which is larger than that expected for J = 7/2 of Eu(²+ ) (17.3 J K⁻¹ mol⁻¹). This is in good agreement with the magnetic entropy deduced from the interconfigurational fluctuation model, which explains the valence transition in Eu(Pd(₁- x)Pt(x))₂Si₂. The application of pressure shifts T₁ and T₂ higher and suppresses the intermediate phase (β phase, T₂ < T < T₁), whereas it does not change the properties of the low-temperature phase (γ phase, T < T₂) and the T(N).
authors.affiliation: Department of Physics, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan. 3da@phys.kyushu-u.ac.jp
authors.forename: A
authors.initials: A
authors.lastname: Mitsuda
authors.forename: T
authors.initials: T
authors.lastname: Okuma
authors.forename: K
authors.initials: K
authors.lastname: Sato
authors.forename: K
authors.initials: K
authors.lastname: Suga
authors.forename: Y
authors.initials: Y
authors.lastname: Narumi
authors.forename: K
authors.initials: K
authors.lastname: Kindo
authors.forename: H
authors.initials: H
authors.lastname: Wada